Excavating is employed to create mines, quarries, etc., in order to obtain desirable material such as ore or stone. In addition to using various types of heavy excavating equipment, drill-and-blast operations are commonly used to fragment material so it can be loaded and hauled. For example, overburden may need to be removed in order to reach the desirable material. Also, once the desirable material is reached, production ore may be removed to be crushed or milled to an acceptable grade. In an open pit mine, drill-and-blast operations may include drilling different types of blast holes. For example, such operations may include drilling production holes, buffer holes, and pre-split holes. These blast holes may be drilled on a work surface designated a “bench” below a sloped surface referred to as a “highwall.”
Production holes are typically vertical, although they also may be at an angle, while pre-split holes are typically at an angle that aligns with the slope of the highwall, for example 5 to 15 degrees from vertical and near to the base of the highwall. In addition, production holes typically are larger in diameter than pre-split holes. Production holes are usually bored by a platform based rotary blast hole drill with a mast at one end of the platform. While a typical platform based drill may be able to drill holes at a positive angle by tilting the mast from a machine vertical position to an angular position with the upper portion of the mast leaning back toward the end of the platform opposite the drill end, it is not capable of achieving a desired negative angle (i.e., tilting the mast away from the end of the platform opposite the drill) for drilling pre-split near the highwall base which would require the drilling end of the machine to be positioned against the highwall.
Current drill-and-blast operations employ platform based drills to bore the typically larger production holes, but not for boring the typically smaller pre-split holes. Pre-split holes are formed close to the highwall and substantially at the angle of the highwall in order to maintain the desired slope of the highwall as the depth of the bench is increased and the height of the highwall is increased. Since platform based drills are not capable of drilling at the required angle of the highwall near the base of the highwall, the usual drill-and-blast operation will employ various dedicated pre-split drills that are usually boom mounted drills. Accordingly, a drill-and-blast operation in an open pit mine ordinarily may require a diverse fleet of drilling machines in order to form the different types of required holes.
There exists a need for a more universal platform based drill. It would be both beneficial and desirable to provide a platform based drill that is capable of boring both vertical and positive angle production hole, and also is capable of boring angle pre-split holes in close proximity to the highwall. In this way, among other advantages, the requirement for securing diverse types of drilling equipment at a mine site may be substantially reduced resulting in a substantial cost advantage. In other words the various types of blast holes, such as production holes, buffer holes, and negative angle pre-split holes, advantageously may be drilled by a single type of drilling machine.
One type of drilling machine used for drill-and-blast operations is disclosed in U.S. Pat. No. 3,181,630 issued to Coburn on May 4, 1965 (“the '630 patent”). The '630 patent discloses a self-propelled rotary blast hole drilling machine wherein a mobile base is rotatably supported at its central portion on a crawler support frame. In a drilling operation, the base is supported by three spaced hydraulic leveling jacks for leveling and supporting the base. The '630 patent includes an elongated one-piece derrick unit pivotally mounted at its lower end to a forward portion of the base. The derrick is supported on the base such that the derrick may be located in either a vertical position for drilling vertical holes, or in an inclined position for drilling angle holes.
While the drilling machine of the '630 patent may be useful for vertical drilling and, to some extent, angle drilling, it lacks the capability to drill blast holes, such as pre-split holes, at a negative angle in close proximity to a sloping highwall. In fact, the drilling machine of the '630 patent is not capable of drilling at a negative angle at all. The '630 patent does disclose, in FIG. 1 and the accompanying description thereof, that the derrick may be inclined via a hydraulic cylinder for drilling blast holes at an angle to the vertical. However, the inclination is such that the top portion of the derrick is moved toward the non-drilling side of the drilling machine, with the drill itself and the borehole angling away from the drilling machine. In other words, the machine of the '630 patent may drill holes at a positive angle, but is not capable of drilling holes at a negative angle, either in close proximity to a highwall or otherwise.
The disclosed platform based drill capable of negative angle drilling of the present disclosure solves one or more of the problems set forth above and/or other problems of the prior art.